Creativity and invention exemplified in the development of a new instrument

A new instrument for nondestructive testing of metals uses a four-point probe and a sensitive electronics package to measure the resistivity and to detect cracks and voids. Both the development of the instrument and its implementation as a product are relatively well documented. The inventive process was very brief and straightforward. An attempt is made to explore what was the inventive act in the development of this instrument, and what made the invention occur when it did. It is concluded that both the technology and the user needs were well established and widely known for at least 15 years before the inventors came along and put the pieces together; thus the key ingredient added in 1982 was the inventor